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<html lang="en">
<head>
    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>结构伪类选择器</title>
    <style>
p:nth-child(1){background-color: rgb(169, 223, 190);}
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</head>
<body>
    <h1>en</h1>
    <p>p1</p>
    <p>p2</p>
    <p>p3</p>
    <ul>
        <li>
            <p>p4</p>
        </li>
        <li>
            <p>p5</p>
        </li>
        <li>
            <p>p6</p>
        </li> 
    </ul>
    <p>p7</p>
    
</body>
</html>